<!DOCTYPE html>
<html lang="en">
<head>
    <style>
	.container {
	    position: relative;
	}
	.main {
	    height: 400px;
	    margin: 0 120px;
	    background-color: green;
	}
	.left {
	    position: absolute;
	    width: 100px;
	    height: 300px;
	    left: 0;
	    top: 0;
	    background-color: red;
	}
	.right {
	    position: absolute;
	    width: 100px;
	    height: 300px;
	    background-color: blue;
        right: 0;
	    top: 0;
	}
    </style>
</head>
<body>
    <div class="container">
    <div class="main"></div>
	<div class="left"></div>
	<div class="right"></div>
    </div>
</body>
</html>